Cold cathode discharge device



Filed Jan. 25, 1958 J R m W N J mz m mw mm M! m M. w n n Ts E 1 m m 14/. N EE WW i muw ATTORNEY United States Patent "ice 3,047,764 COLD CATHODE DISCHARGE DEVICE Robert A. Lee, Locust, and Keith W. Olson, Neptune,

N.J., assignors to The Bendix Corporation, a corporation of Delaware Filed Jan. 23, 1958, Ser. No. 710,689 3 Claims. (Cl. 313-220) The present invention relates to electron discharge devices and more particularly to electron discharge devices of the cold cathode gas filled type. i

Heretofore, cold cathode trigger tubes, which utilize low work function cathodes and provide high pealccurrents, have been made with glass envelopes of relatively large outlines. Such tubes are limited in the ability to Withstand shock and vibration by the limitations of the glass envelope.

It is desirable to have an extremely rugged device capable of supplying a high peak current, such as 50 to 100 arnperes, with an anode hold of at least 2000 volts, in a size as small as possible, consistent with the neces sary required leakage paths.

The present invention provides a cold cathode electron discharge device utilizing a stacked ceramic design wh ch is small in size, rugged and capable of supplying high peak currents. By the utilization of a stacked construction, the brazing operations are performed prior to the insertion of the low work function cathode thus permitting the use of a ceramic envelope.

It is an object of the invention to provide an improved electron discharge device.

Another object of the invention is to provide a novel method of fabricating an electron discharge device.

Another object of the invention is to provide a novel cold cathode electron discharge device of small physical size capable of supplying high peak currents.

Another object of the invention is to provide a novel ceramic metal cold cathode electron discharge device.

Another object of the invention is to provide a novel cold cathode electron discharge device utilizing a stacked ceramic design for simplification of construction and to provide ruggedness.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing, wherein three embodiments are illustrated by way of examples.

In the drawing:

FIGURE 1 is a sectional view of a device illustrating one embodiment of the invention.

FIGURE 2 is a sectional view of a device illustrating another embodiment of the invention.

FIGURE 3 illustrates a further embodiment of the invention.

In the drawing, like parts, in the various figures, have been assigned the same reference numerals for simplicity. Referring now to FIGURE 1 wherein a cold cathode electron device is indicated generally by the numeral 11 and includes an envelope 12, cathode 13, anode 14 and control electrodm 15 and 16.

The cathode 13, which may be of the type disclosed in US. Patent 2,604,603, comprises a cathode cup 17, preferably made of nickel, in which a low work function cathode pill 18 is contained. The pill 18 is made by compressing cesium chloride, aluminum powder and nickel filings into the desired form. The pill 18 is held within the cup 17 by a wire mesh screen 19, preferably made of nickel. The cathode cup 17 is secured to a metallic inverted cup shaped member 20 by welding. While cesium chloride has been illustrated, it is understood that other low work function materials may be used, such as the alkali metals, the earth alkali metals, or the rare earth vided between the button 21 and anode 14 by metalizing the ceramic and brazing the members together. The anode 14 also serves as the exhaust tubulation, and after the device has been processed, is sealed off in a conventional manner. The button 21 has a raised portion 23 for providing additional mechanical strength and also to provide a longer leakage path between the anode 14 and the grid 15 which is of an inverted cup shaped configuration. An opening 24 concentric with the anode 14 is provided in the grid 15. A flanged portion 25 is brazed between the button 21 and a ceramic cylinder 26 to form a vacuum tight joint between the members.

The elect-rode 16 which may be a flat ring-shaped member is brazed between the cylinder 26 and ceramic cylinder 27 by metalizing the contacting surface of the cylinders 26 and 27 and brazed with electrode 16 to form a vacuum tight joint. Secured to the cylinder 27 and telescoping a portion thereof is a metallic ring 28. The ring 28 is brazed in like manner to provide a vacuum tight seal with the cylinder 27. The cup shaped member 20 is inserted into the cylinder 28 after all the brazing operations'have been performed and is sealed thereto by a weld 29 thus completing a vacuum tight enclosure.

The aforenoted structure permits the assembly and high temperature brazing operations to be performed before the cathode is inserted in the device. This prevents the cathode from being damaged by the high temperatures necessary for the brazing of the parts.

In FIGURE 2, the cathode 13, cup 17, pill 18, screen 19 and inverted cup 20 are similar to those disclosed and described for FIGURE 1, hence a detailed description thereof will be omitted. The hollow anode 14 extends into a cup shaped ceramic member 30 and a vacuum tight joint is formed therebetween by nietalizing the contacting surface of the ceramic cup 30 and brazing to the anode 14. A flat disk like control electrode 31 is brazed in like manner between the cup 30 and a ceramic cup 32 to form a vacuum tight unitary structure. The electrode 31 has an opening 33 therein and positioned such that the opening 33 is concentric with the anode 14. A tab 34 may be provided on the electrode 31 for making electrical connections therewith. It is understood, however, that electrical connections may be made by other conventional methods.

The cup 32 has a radially extending flanged or bottom portion 35 which has an opening 36 which is positioned concentric with the anode 14 and covers all but a small portion of the electrode 31, thus shielding it from sputtered cathode material. A metallic ring 28 is positioned over the cup 32 and secured thereto in like manner as in FIGURE 1. A keep alive electrode 37 may be provided which extends through and is brazed with the member 32. The cathode cup 20, together with the cathode assembly, is then placed into the ring 28 and sealed thereto by a weld 29 as described for FIGURE 1.

In FIGURE 3 the construction is somewhat similar to that shown in FIGURE 2, hence only the differences will be described in detail. Instead of the disk like electrode 31, the flange portion 35 of the member 32 is provided with a metalized coating 40, a portion of which is extended into the opening 36. A conductor 41 may be provided to form an electrical connection.

Thus, the aforenoted construction provides an extremely rugged unit capable of supplying a high ampere peak current with good anode hold-01f characteristics and of a small physical size. Further, the method of fabricating Patented July 31, 1962.

is such that the cathode is not subject to high temperatures which would cause deterioration thereof.

Although only three embodiments of the invention have been illustrated and described, various changes in the form and relative arrangement of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention.

What is claimed is:

1. An electron discharge device comprising a substantially cup shaped ceramic envelope, an anode extending through and brazed with said cup shaped envelope at the closed end thereof, a control grid positioned adjacent to said anode, a circular flange having a portion telescoping and brazed to the open end of said cup shaped envelope, a cup shaped member having a cathode secured to the underside thereof positioned within said circular flange, and means sealing said flange with said cup shaped member near the open end of the latter to form a vacuum tight structure for said device.

2. An electron discharge device comprising a first cup shaped ceramic member, an anode extending through the bottom portion of said first cup shaped member and brazed therewith, a second cup shaped ceramic member having an opening in the bottom portion concentric with said anode, a disk like control grid positioned between said ceramic members and brazed thereto to form a unitary structure, said grid having an opening therein concentric with said anode, a cylindrical flange having a portion surrounding and brazed to said second cup shaped member adjacent to the open end thereof, a cathode as- 4 sembly including a metallic cup shaped member proportioned to fit Within said cylindrical flange around their outer edges thereof, and means sealing said metallic cup shaped member with said cylindrical flange to form a vacuum tight enclosure.

3. An electron discharge device comprising a first cup shaped ceramic member, an anode extending through the bottom portion of said first cup shaped member and brazed therewith, a second cup shaped ceramic member having an opening in the bottom portion thereof, and positioned in stacked relationship with and brazed to said first cup shaped member with said opening concentric with said anode, a metallic coating on the underside of said second cup shaped member forming a control grid for said device, a metallic ring surrounding the open end of said second ceramic cup shaped member and brazed therewith, a cathode assembly including a flanged member adapted to fit within said ring, and means sealing said ring with said flanged member.

References Cited in the file of this patent UNITED STATES PATENTS 2,451,297 Moore Oct. 12, 1948 2,604,603 McLinden July 2-2, 1952 2,643,332 Diemer June 23, 1953 2,647,218 Sorg et al. July 28, 1953 2,722,624 Doolittle Nov. 1, 1955 2,731,578 McCullough Jan. 17, 1956 2,840,746 Price June 24, 1958 

